1. Field of the Invention
The present invention relates to a lens periphery processing method and a lens periphery processing machine for processing an eyeglasses lens, based on lens frame shape data measured by contacting a contact element with a V shaped groove having V shape, formed in the inner face of a lens frame for eyeglasses lens, and the lens for eyeglasses made by those.
2. Description of the Prior Art
Generally, a lens frame which constitutes an eyeglasses frame, is formed with a V shaped groove formed in the inner face thereof, having a pair of inclined faces with its cross section having a V shape.
FIG. 9A is a sectional view, in which a lens frame 1 of an eyeglasses frame (the whole part thereof is omitted) is cut in the direction perpendicular to the frame extending direction. A V shaped groove 1d which has inclined faces 1b and 1c composing a V shape, formed in an inner face 1a of a lens frame 1, opens at a given opening angle xcex81 from a bottom 1e of the V shaped groove toward the V shaped groove edges 1f and 1g. The opening angle xcex81 and a depth H of the V shaped groove, differ slightly depending on the shape, material, manufacturer, and the like of the lens frame 1.
Generally, the shape of the lens frame 1 is measured by contacting a contact element 2 (see FIG. 8A) provided on a frame shape measuring instrument etc., not shown, into contact with the V shaped groove 1d. 
The contact element 2 is provided with a tip end portion having an abacus bead shape, needle shape, spherical shape, rectangular shape, or the like (see Japanese Patent Application Laid-Open Nos. 51-119580, 58-196407, 58-38919, 60-52249, 62-88402, 63-24106, and 10-113853).
The contact element 2 shown in FIG. 8A has inclined faces 2a and 2b open at an angle xcex82 and it is inserted in the V shaped groove 1d so that the points in the tip end portion thereof comes into contact with the V shaped groove edges 1f and 1g at the same time.
On the other hand, as shown in FIG. 9B, at the periphery of an eyeglasses lens 3 which is framed in the above described lens frame 1, there is formed a V shaped portion 3d having a pair of inclined faces 3b and 3c inclined at an opening angle xcex83 (almost the same angle as the above described angle xcex82) from a vertex 3a of the V shaped portion based on the lens frame shape data of the lens frame 1 measured with the above described contact element.
In this specification hereafter, the portion of eyeglass lens by which the eyeglass lens is correspondingly put into and held by above described V shaped groove, is referred to as the xe2x80x9cV shaped portionxe2x80x9d as above though actual cross section of the portion in accordance with this invention is rather not triangle.
On the sides of a lens front face 3e and lens rear face 3f of the V shaped portion 3d, a V shaped portion shoulder 3i ranging from the inclined face 3b of the V shaped portion 3d to a lens front edge 3g, and a V shaped portion shoulder 3j ranging from the inclined face 3c to a lens rear edge 3h, which have a width different according to the peripheral point of the eyeglasses lens 3, are formed at the same time that the V shaped portion 3d is formed. The above described whole construction is referred to as a V shaped portion in this specification.
As shown in FIG. 8B, this V shaped portion is formed by using a grinding wheel 4 having the inclined faces 4a and 4b opening at an angle xcex84 (almost the same angle as the above described angles xcex82 and xcex83, for example, about 120 degrees).
On the eyeglasses lens 3 having been formed with the V shaped portion, the opening angle xcex82 of the contact element 2 is approximately equal to the opening angle xcex83 of the V shaped portion 3d. Therefore, as shown in FIG. 8C, the inclined faces 3c and 3d come into contact with the V shaped groove edges 1f and 1g in a state in which the a portion around vertex 3a of the V shaped portion 3d intrudes into the V shaped groove 1d, by which the eyeglasses lens 3 is framed in the lens frame 1.
The above described prior art has problems as described below. The opening angle xcex81 of the V shaped groove 1d formed in the lens frame 1 of eyeglasses frame, is not fixed and different according to eyeglasses frame, as described above.
On the other hand, the opening angle xcex84 of the grinding wheel 4 for processing the V shaped portion of eyeglasses lens, has a predetermined angle, so that the opening angle xcex83 of the V shaped portion 3d which is formed at the lens periphery of the eyeglasses lens 3 and processed with the grinding wheel 4, is formed so as to be approximately equal to the opening angle xcex84 of the grinding wheel 4. Therefore, the V shaped portion 3d has a predetermined angle.
For this reason, when the eyeglasses lens 3 is framed in the V shaped groove 1d, because it has the V shaped portion 3d processed with the opening angle xcex83, the eyeglasses lens 3 can not be framed in a state in which the vertex 3a is in contact with the V shaped groove bottom 1e of the V shaped groove 1d. As shown in FIG. 8C, the V shaped groove edges lf and lg of the V shaped groove 1d in the lens frame 1, come into contact with the inclined faces 3b and 3c of the V shaped portion 3d. 
However, the eyeglasses lens in this state is merely held only at the V shaped groove edges 1f and 1g of the eyeglasses frame, strong holding has not been expectable.
The reason for this is that since the opening angle xcex83 of the V shaped portion 3d is formed so as to be approximately equal to the opening angle xcex84 of the grinding wheel 4 (V shaped portion forming grinding wheel), the lens frame shape data is obtained by the contact element 2 having the opening angle xcex82 which is approximately equal to the opening angle xcex84 of the grinding wheel 4 (V shaped portion forming grinding wheel) in order to make the eyeglasses lens capable of being framed in any kind of the V shaped groove 1d of all eyeglass.
Because the eyeglasses frame is measured in this state on the lens frame itself, which is different from the V shape groove that the V shaped portion is actually held in. Even when the lens with the V shaped portion is processed based on this measurement, the lens periphery that can be strongly held in the eyeglasses frame, is not realized.
Also, it is preferable that the tip end width (thickness) w of the contact element 2 is made equal to or larger than a width W of the lens frame 1 of eyeglasses frame in order for the eyeglasses lens to be framed in the eyeglasses frame in which the opening angle xcex81 and the depth H of the V shaped groove, are different variously.
However, for the reason of the construction of lens frame shape measuring instrument, the lens frame 1 must be fixed so as to withstand the measurement pressure of the contact element 2, the tip end width (thickness) w of the contact element 2 could not be made equal to or larger than the width W of the lens frame 1 of eyeglasses frame because of prevention for the interference between a holding means for fixing the lens frame 1 and the tip end width (thickness) w of the contact element 2.
The present invention has been made to solve the above problems, and accordingly an object thereof is to provide a lens periphery processing method, a lens periphery processing machine and lens for eyeglass, in which a V shaped portion that fits strongly in a lens frame of eyeglasses frame, can be processed in such a manner that V shaped portion contact with inside of the V shaped groove of the lens frame so that a contact element does not interfere with a holding means for fixing and holding a lens frame, and even if the V shaped groove is measured in a state when the lens frame is tilted, a difference in size due to holding position between the lens frame and a processed eyeglasses lens, does not arise.
To achieve the above object, the lens periphery processing method according to a first aspect of the present invention is characterized by comprising the steps of: measuring a lens frame shape of an eyeglasses frame by contacting a contact element at both sides of a V shaped groove formed in the inner face of a lens frame of an eyeglasses frame; and forming V shaped portion of said eyeglasses lens in a shape that the eyeglasses lens for said eyeglasses frame is put into said V shaped groove with contacting at the points where said contact element contacted on said both sides of the groove, as substantially the deepest contacting points in the groove.
The lens periphery processing machine according to a second aspect of the present invention is characterized by comprising: lens frame shape measuring means having a contact element contacting on both sides of a V shaped groove formed in the inner face of a lens frame of eyeglasses frame; and grinding means for processing a V shaped portion of lens for said eyeglasses frame based on lens frame shape data from said lens frame shape measuring means, wherein said grinding means forms V shaped portion of said eyeglasses lens in a shape that the eyeglasses lens for said eyeglasses frame is put into said V shaped groove with contacting at the points where said contact element contacted on said both sides of the groove, as substantially the deepest contacting points in the groove.
The lens periphery processing machine according to a third aspect of the present invention is characterized in that the grinding means has a grinding wheel having a processing tooth form of a shape for forming a tip end shape of the V shaped portion.
The eyeglasses lens according to a fourth aspect of the present invention is characterized in that the cross section of V shaped portion thereof is formed in a shape other than triangle, which is put into a V shaped groove formed at inner face of lens frame of said eyeglasses, with contacting on both sides of said V shaped groove.